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Provides the implementation of the Telemetry Language <em>function</em> 
construct, which accepts an array of either
Number, String, and/or TelemetryStreamCollection objects, 
and returns either a Number or TelemetryStreamCollection object.
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There are two kinds of telemetry functions: built-in (or "stock") functions and additional custom
functions defined using the telemetry extension point.  
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An external client normally should
not use any classes in this package except those required to supply the definition of additional
functions. Otherwise, the intended client of this package is 
<code>TelemetryEvaluator</code>. All function invocations are done through 
<code>TelemetryFunctionManager</code> interface. 
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